Television and like system



I 1929- J-. I... BAIRD 1,735,946,

TELEVISION AND LIKE SYSTEM Filed 192'! 2 Sheets-Sheet. l

Nov. 19, I929. J. L. BAIRD 1 ,735,946

TELEVISION AND LIKE-SYSTEM Filed Oct. 7/1927 "2 Sheets-Sheet 2 JOHN LOGIE namn,

Patented Nov. 19,- 1929 I OF IlONDON, ENGLAND, ASSIGNOR TO TELEVISION LIMITED, OF

LONDON, ENGLAND, A BRITISH COMPANY TELEVISION AND LIKE srs'rnm Application filed ctober' 7, 1927,

This invention is for improvements in orrelating to television and likesyste'ms, and has for its object to provide an improved method and apparatus for the process or step of exploration which is usedin such systems.

The invention relates to that type of system in which an image at the transmitting station is traversed relatively to 'a light-sensitive cell soas to expose in'succession all partsof the image to the cell, andto the similar method and apparatusat the receiving station whereby an image is reconstituted by an inversion of the exploring process. A traversal is effeoted by moving the image. across the cell so that the latter scans a narrow band of the image. The image isexplored by effecting a series of traversals by shifting the cell or the image laterall a distance equal to the width of the band a ter each traversal, this process being repeated until the whole area of the image-has been explored in a series of parallel bands. It will further be understoodthat the movements of the image and cell are merely relative movements, and in some cases the movement may be only a virtual one, as for example when exposing a stationary image to a stationary cell through a series of holes in a rotating disc, each hole exposing by its movement a different band of the image.

Heretofore such exploration has been carried out by successive traversals which were all alike in direction and sense, but according to the present invention difl'erent traversals are made in difl'erent directions.

This invention also comprises a method of exploration wherein either or each component of the traversing movement is reversed in direction in defi'erent traversals.

According to yet another feature of thisinvention, the inclination to a datum line, such for example as an edgeof the picture, of either or each component of the traversing I movement, is changed for different traversals; it may, for example,.be changed for each successive traversal. a

This invention alsocovers in television or like systems for transmitting pictures and the like, the simultaneous superimposition of images produced by explorations indifferent di rections. Thus, for example,

that indicated at 12, which is at the greatest two complete 1 100 Serial No. 224,710, and in Great Britain October 15, 1926.

images produced by explorations in di fierent directions may be superimposed one on the other, or if the bands of one traversal are parallel with the bands of another traversal, each traversal may supplyalternate bands, the two sets of bands being intercalated with one another to produce a complete image.

This invention also comprises various con.-

structional forms of exploring device for carrying out the method hereinbefore set forth. y

In the accompanying drawings, whichare purely diagrammatic, each figure represents a particular form of exploring device.

Theinvention may be applied to various. types of exploring devices, such for example as a rotating disc with holes in it, which holes expose a small portion of the stationary image whilst they are opposite to it or the slotted discs type of exploring device; or a rotating disc having a series of lenses each of which projects an image and sweeps it across the light-sensitive cell; or other equivalent arrangements with moving bands, rotating. mirror p'olyhedrons, concave mirrors, or combinations of such devices.

For simplicity in illustrations, Figures 1 I periodically reversing the direction of tra-.

versal;

, Figure 10 illustrates diagrammatically the direction of traversal effected by certain of the. modified forms of scanning device, particularly that illustrated in Figure 7 of the. drawings. In Figure 1, 10 represents a disc mounted on a shaft 11 so as to be rotatable at an apropriate speed. This disc has two sets of 1 oles'in it arranged in spirals of opposite pitch; One set of holes, commencing with distance from the shaft 11, lies on a spira way round the disc, so that the 11013,?14 is the nearest of them to the shaft 11. The second set of holes, arranged from 14 round the remainder of the disc to the hole 12, lies on a spiral indicated by the line15 which is of opposite pitch to the spiral 13. Assumthat the disc is rotating in the direction icated by the arrow 16, and that the image which is-to be explored is at 17, the spiral 13 of holes gives a series of bands of which the length of the bands is in' the direction of thearrow 18, and the successive bands are spaced from one another in the direction of the arrow 19. That is to say, the two componentsof the exploration by the spiral 13 are in the directions 18, 19 respectively.

The spiral 15 gives bands of which the lengths are inthe direction of the arrow 18 but the bands are spaced apart successively .in the direction of the arrow 20 which is opposite to that of the arrow 19, or in other i words, the spiral 15 has the direction of one successive traversals are in tlons.

of its components reversed with respect to that of the spiral 13, and since each spiral gives a comp ete traversal of theimage, the

opposite direc- Figure2 shows a modification in which each of the spiral sets of holes extends completely around the disc instead of only halfway round it. One spiral starting from the combination of the constructions of hole 21 extends in'a anti-clockwise'direction as indicated by t e line 22 to the hole 23, and the other spiral extends from the hole 21 in a clockwise direction, as indicated by the line24. The holes for the two spirals are interealated in order that the single light-i sensitive cell can explore the whole picture; it will be seen that when the disc is rotating in the direction indicated by the arrow 25, the spiral 22 provides a series of bands whose length lies in the direction indicated by the arrow 26 and the bands appear successively the direction of the arrow 27 The spiral. 24, on the other hand, provides'bands whose length is in the direction of the arrow 26, but they appear successively in the direction of the arrow 28. Moreover, the bands appear alternately, first one on the right, then one on the left, the first image being built -up from the right towards the left and the second from the left towards the right. Each image maybe complete in itself and the two images simultaneously superposed, or each spiral may provide only alternate bands, so that the two sets of hands together constitute a complete image or picture.

Figure 3 shows a modification in which a two-partspiral '29, 30 similar to the arrangement shown in Figure '1, is associated with a second similar spiral, 31, 32, being in effect a Figures 1 and 2.

It will be seen that when the two spirals .thedirection of the arrow of opposite pitch are arranged on a single disc only the second component of the exploration movement is altered. By arranging the spirals oneccentric discs as shown in Figure'4,

the directions of the length of the bands can 7 be'altered. In --F igure 4 adisc 33rotating in the direction indicated bv the arrow 34 has a spiral of holes 35 extending half-way-roundit, and this disc gives an exploration in which the lengths of the bands lie inthe direction of the arrow'36 and the successive bands'follow one another in the direc -1 of the arrow 37. A second disc 38 with a sim1 ar spiral of holes 39 is arranged to rotate abou another axis in gives an exploration in which the length of the bands is in. the direction of the'arrow 41,

and this disc i of the second set of bands is therefore inclined to, and in the arrangement illustrated is substantially at right-angles to, the length of the handset the first. By' reversing the direction of rotation of the disc 38, it will be appreciated that the arrow 42 indicating the successive spacing of the second set of bands calf-also be reversed. Since the explorations provided by the-two discs 33,38 have to follow one another successively, each disc is cut away over substantially half its circumference, or is slotted as at 43, 44 in order to expose the image to the other disc.

Exploring devices are known comprising two radially slotted rotatable discs rotating about different axes'so positioned that the slots cross one another in front of the image.

One of the discs is made to rotate comparatively slowly w'th respectto the other, and

its slots define e direction of the length of the bands produced by this method of exploration. The present invention can be applied to this type of exploring device by arranging the slots on the slower-moving (1186 in a zi zag or other formation such that they are di ferently Incline to some datum line, such for example as the edge of the ieture. Such an arrangement is illustrated 1n Figure 5 in which the disc 45 is provided with a series of radial slots 46 and the disc 47 is provided with a series of slots arranged in zig-zagformation as shown at 48. Whilst one of the slots 48 is moving a distance equal to its width, one of the slots 46'sweeps across it,

thereby tracing out one band or strip of the" image. The next slot 46 traces out the next succeeding band, and so on, until one traversal is completed. The next slot. 48 then comes into operation and defines the series of bands for the-next traversal, and since the second slot 48 lies at'an'angle to the first slot 48, the

' successive explorations take place in different directions.

'preciated that Figure 6 'illustrates yet another arrangement of exploring device comprising two discs 49, ,50. Each disc is provided with two sets of spiral holes indicated by the lines 51, 52 and 53, 54 respectively, and each disc also carries a spirally arranged set of slots adapted to expose the holes on the other'disc when these holes in turn pass across the area 55 definin the picturetto be transmitted. The two iscs rotate in the same direction about parallel axes, so that the holes on one disc pass downwards across this area' and the holes on the other disc pass upwards across it thereby exploring the bands in opposite directions. With the arrangement illustrated each disc explores alternate bands of the picture, so that the two sets of bands together make upthe complete picture. It will be apthe arrangement of the holes and slots must be such as to expose only one hole at any instant unless provision is made for the simultaneous exploration of diiferent sections of the picture simultaneously, by means of an appropriate number of light-sensitive cells. 1 I

Figure 7 shows an arrangement of two discs each with its own spiral of holes and a set ofslots in each disc to co-operate with the holes in the other disc,,the ar'rangementbeing such that-the bands explored by the one disc are at right-an es to the bands explored by the other disc. With this arrangement the distortion is reduced to a minimum and the maximum amount of detail is shown in the picture.

' Figure 7 illustrates diagrammatically the path of the scanning lines obtained by the use of the device illustrated in Fig. 7. It will be noted thatthe exploration is effected first in one direction and then in the other by a1- ternate discs, the successive directions of tra V- ersal being indicated by the reference characters 58 to 63 inclusive. By altering the relativepositions of the apertures and slots in I the two discsthe succession of the various traversing lines may be correspondingly al-- tered, and it is understood that the inven tion is not limited to the precise method 0 exploration illustrated in Fig. 10.

As above stated, lensed holes may be substituted for-the simple openings in the disc of'the-expl'oring device, and Figure 8 shows a'construction, in which two dISCS are each provided with a spiral of lenses, the arrange- .ment being such that the picture is explored in vertical bands by one of the discs and horizontal bands by the other disc.

' It also lies withinthe scope of this invention to effect the exploration in two'difierent directions,' by using two separate'light-sensh tive or photoelectric cells, one for each direction of exploration. One example of this arrangement is illustrated diagrammatically in Fi re 9 in which two separate images of the ob ect are used one for. each exploring disc.

are preferably produced as closely side by side as possible so that they will be substantiall identical with one-another, and the two exp oring discs indicated at 56, 57 are provided with a spiral of holes or lenses so as respectively to explore the two images in bands at right-angles to one another. With this arrangement the two explorations can proceed simultaneously, that is to' say, during. the explorin of a horizontal band on one image, a vertical band can be simultaneously explored on the other image. The two images are simultaneously transmitted to the receiving stationand there superimposed one upon the other. I

It will be appreciated that mirrors may be used instead of holes or lenses on the discs-- The two images as is usual with this type of exploring device.

In all the constructions embodymg two discs which are required to rotate in the same direction, it is desirable that these discs should rotate in absolute synchronism w1th one another and this is preferably effected by directly coupling them together, as for example by means of two coupling-rods on cranks which are inclined, say, .at rightrangles to one another an alternative method of connecting them is to use a single crank on each disc and a third idler crank which is displaced from the line joining the two shafts and coupling all three cranks .by= -means ot a single rigid triangular connecting rod. This construction provides a'connection -which has no dead centre. 1

' It will be appreciated that this exploring device can be used for exploring a' picture by means of a light-sensitive cell or cells at the transmitting station, and can also be used for reconstituting an image onthe picture at the receiving station.

This inventlon also covers the use'of a disc I having a zi'g-zag arrangement of slots as shown at 47 48 at the receiving station of a television system, as a spotting device. If a spot of light be cast on the object or v1 ew which is being transmitted, and the receiving v station be provided with a'disc similar to the 1 f disc147 instead of or in addition to the usual device, the spot of light will be reproduced as a luminous cross which can be more easily located than an image of the spot of light. This arrangement is of value for military purposes, particularly when used in combination with a beam of light which is outside the visible spectrum.

1. In televisionapparatus, the combination i with a light sensitive device, of means for ejx-. ploring an ner that successive traversals are made in directions which are at right angles;

2. In television apparatus, the'combination with a light sensitive device, of means for scanning an object by said device, 'sai'dmeans comprising a pairof rotatable discs, one of explor'in said discs serving to explore the object by a series of traversals in one direction, and the other disc serving to explore the object by a series of traversals in'a direction at right angles thereto.

made by alternate discs.

4. In television apparatus, the combination with a light sensitive device, of means for scanning an object by said device, said means comprising a pair of rotatable discs, each provided with a series of apertures s'o disposed that successive traversals of the object are made by alternate discs, and are angularly related in direction;

5. In television apparatus, a pair of rotatable discs for exploring an object, eachdisc being provided with a series of spirally disposed apertures, said discs being so positioned with relation to each other as to produce peri- Odie alignment of certain of the apertures in the two discs. '6. In television apparatuaa pair of rotata- .ble discs for exploring an object, each disc being provided with a series of spirally disposed apertures, the axes of the discs being .spaced apart whereby one disc efi'ects traversals of the object in a direction at an angle to the traversals effected by the other.

7. In television apparatus, a pair of rotatable discs for'exploring an object, each disc being provided with a series of spirally disposed apertures, the axes of the discs'being so related to the optical axis of the system that the apertures. in one disc traverse the object in a direction substantially at right angles to those of the other disc.

'8. In television apparatus, a pair of rotatable discs for exploringan object, each disc being provided with aseries of spirally disposedapertures, the axes of the discs being disc being provided with a series of spirally disposed apertures, the axes of the discs being so related to the optical axis of the system that the apertures in one disc traverse the object in a direction substantially at right angles to'those of the other disc, successive traversals being effected by alternate discs,

and a series of slots in each disc. alternating so related to the optical axis of the system that-the apertures in one traverse the object in a direction substantially at right angles to those of the other disc, successive traversals being effected by alternate discs.

9. In'television apparatus, a; pair ofrotata- I ble discs, each disc being provided with a series of spirally'disposed apertures, and-a series of slots, said iscs being so disposed with relationto each-other as to produce isc v riodic alignmentof'th'e apertures in one with the slots in the other discf i W 10. In television apparatus, a pair of discs @e'ach disc being provided with a series of spirally disposed apertures, and a series of slots,- said apertures and slots being alternately arranged in each disc.-

11. -In television apparatus, a air of ro-' tatable discs for'exploring an o ject, each izo 

